As offshore platforms near the end of their life, their fixed cranes may no longer be operational or may lack sufficient lifting capacity for topside module removal in the decom stage. Modular rental cranes from Thunder Cranes offer an economical and safe solution for topside decommissioning, making the platform lighter in weight and assisting in clean-up operations in preparation for the arrival of heavy lift vessels.
Chevron Thailand engaged Thunder Cranes to assist with the removal of modules from the topside of a production platform located in the Gulf of Thailand. This work was scheduled prior to removal of the entire well-head platform by a heavy lift barge crane. Removing the modules would sufficiently reduce the overall platform weight to within the capacity of the intended barge crane.
The existing platform crane capacity and reach radius was not sufficient for the project. The clients’ objective was a reverse-installation and backloading of various modules to supply vessel for disposal or recycling. Located on the top deck there were 14 large components weighing between 10 to 40 tons, as well as a number smaller components of various weights below 10 tons.
We proposed the TC90 modular rental crane which has a maximum capacity of 50MT for offboard lifts. Our client had explored other options for module removal – such as hiring a barge crane. However, Thunder Cranes’ modular rental crane was the best solution from the viewpoint of ensuring safe, static lifting, as well as from the viewpoint of cost and time savings.
The project called for expert and detailed planning and an extensive site survey enabled our project team to create a detailed proposal and lifting plan for a step-by-step lifting solution.
General arrangement drawing of the proposed TC90 position on the wellhead platform
Challenges & Solutions
Challenge #1 – The platform had very limited space for rigging up and no exposed beams on which we could apply our TC90 clamping system. Therefore welding with dog plates was required to tie down modular crane. This was implemented safely and without any issues within 3 days with one shift of welders for a total rig up time of 6 days including load testing. In addition, due to limited space on the platform deck, the supply vessel was on standby within reach of the platform crane, allowing the rig up and rig down of the TC90 crane on the fly.
Challenge #2 – Some of the larger modules at the limit of the TC90 reach radius did not have verified weight information. A decision had to be made on whether to reposition the crane for those lifts or whether to disassemble and breakdown down those modules into smaller components. Upon further study it was concluded that the best way forwards was to breakdown some of the modules. In addition, we deployed our most experienced lifting superintendent on site to supervise the most critical lifts.
TC90 base beams are tied down to the platform with welded dog plates
Planning
Our process starts with a thorough assessment of the client’s lifting requirements, platform drawings, general specifications, and project timelines. A site visit is then conducted to verify that an appropriate and practical solution can be proposed.
Our proposal and quotation come with a Site Visit Report to clearly communicate the proposed method with drawings and photos.
After the proposal is given the green light, we begin the detailed planning stage where we collaborate with the client to customize elements of the project in terms of materials, equipment, 3rd party services, utilities, scaffolding, etc. Customization can include any platform modifications if needed, or any re-positioning, or removal of elements from the main deck of the platform.
Furthermore, our modular crane configuration is customized to meet specific needs with regards to the tied down method, boom reach radius, zone rating, or any other safety or environmental considerations.
In the next step an engineering work pack is submitted to the client addressing the specific scope of work and lifting requirements, featuring detailed considerations from the site visit, with comprehensive rig up and lifting plans, customized layout and positioning drawings, as well as reaction force calculations needed to conduct a structural analysis.
Pre-mobilization planning includes risk assessment/hazard identification, and alignment sessions are conducted for offshore personnel to ensure safe and efficient operation of the modular cranes.
Depending on the project location, the preparation and deployment of the modular cranes and auxiliary equipment might begin months ahead to ensure cranes are at the load out port and ready to be transported to the offshore site and assembled according to the pre-planned schedule and project configuration.
Timeline
- Load out from port and sailing to platform via supply boat.
- Platform crane lifts TC Modular Crane components to platform for rig up.
- Welding base beam and complete rig up of TC90.
- Inspection and load testing TC90.
- Commence lifting operations.
- Stop operation during heavy monsoon weather.
- Resume lifting operations.
- Rig down TC90 and demob.
Outcome
The project objectives were successfully met to our client’s satisfaction, within schedule and without incidents or hinderances.
Conclusion
By removing the production modules the overall platform weight was reduced to be within the capacity of the heavy lift vessel which was able to remove the topside and structure in one lift.
Application
- Lifting Solution for Topside Decom
Challenges
- Limited space for rig up
- Heaviest lift of 37 tons
- Welding due to no clamping possible
Our Service
- TC90 modular rental crane
- Crane Operators
- Detailed Planning & Preparation
Benefits
- Cost Effective
- Safe Operation
- Timely Execution
Location
- Offshore Thailand